What is the ruling on one who accuses a person of zina and calls him a zaani?

Slandering a Muslim is one of the major sins and one of the seven destructive sins. There is no difference in this regard between slandering a man or a woman. Whoever slanders a free, adult, sane Muslim who is chaste from the indecency with which they were accused, then that slanderer deserves the prescribed punishment for slander. The slandered person has the right to demand that the punishment be carried out, and the ruler must implement it unless the slandered person pardons them.